JP5210990B2 - Mobile communication system, mobile station and radio base station - Google Patents

Description

  The present invention relates to a mobile communication system, a mobile station, and a radio base station.

  In a mobile communication system defined by 3GPP, for example, an LTE (Long Term Evolution) mobile communication system, “PCI (Physical Cell Identity)” and “CGI (Cell Global Identity)” are used as identification information of each cell. It is used.

  In an LTE mobile communication system, a connected mobile station UE performs measurement of neighboring cells, transmits a measurement report regarding the neighboring cells (Measurement Report) to the radio base station eNB, and the radio base station eNB It is assumed that handover control is performed by determining whether the handover is appropriate based on the measurement report.

  However, “CGI” is identification information that can uniquely identify a cell in an LTE mobile communication system, whereas “PCI” corresponds to a scramble code in a WCDMA mobile communication system. It is used repeatedly in a plurality of cells. That is, in the LTE mobile communication system, a cell cannot be uniquely specified only by “PCI”.

  Therefore, when a cell is specified only by “PCI”, there is a problem that a cell recognized by the mobile station UE and a cell recognized by the radio base station eNB may be different during a handover process or the like.

  Therefore, in the LTE mobile communication system, the mobile station UE receives broadcast information (BCCH (Broadcast Channel), MIB (Master Information Block) / SIB (System Information Block)) transmitted in a handover candidate cell. Therefore, it is considered to transmit a measurement report including “CGI” included in the broadcast information.

  Here, in order for the mobile station UE to receive the broadcast information transmitted in the handover candidate cell, a measurement gap (Measurement Gap) is provided between the connected radio base station eNB and the mobile station UE. Need to be.

  In addition, if the report of “CGI” to the radio base station eNB is delayed, there is a possibility that a situation such as RLF (Radio Link Failure) or failure of handover control may occur.

  Further, in the LTE system, a CS (Circuit Switched) service is not provided, and all are PS (Packet Switched) services. Therefore, in order to provide the CS service, it is necessary to switch the connection of the mobile station UE to a radio base station of a radio access scheme (for example, UMTS scheme or GSM scheme) that supports the CS domain. This procedure is called “CSFB”.

  When performing CSFB in an LTE mobile communication system, the mobile station UE transmits a measurement report including a result of a handover candidate cell to the connected radio base station eNB, and the radio base station eNB It is assumed that a handover destination cell is determined based on the measurement report and the CSFB procedure for the cell is executed. In order to measure a cell of a different RAT (Radio Access Technology), the above-described measurement gap is required.

  Here, if transmission of the measurement report to the radio base station eNB is delayed, the CS transmission / reception time becomes long, which is not desirable for the user experience.

  In LTE Release 8, two types of measurement gap patterns shown in FIGS. 7A and 7B are defined.

3GPP TS36.331 v8.6.0 3GPP TS36.304 v8.6.0

  However, in the measurement gap pattern defined in LTE Release 8, as shown in FIGS. 7A and 7B, the duty ratio of the measurement gap is low (6/40 or 6/80). Therefore, it takes a long time to measure a handover candidate cell.

  In the LTE mobile communication system, the transmission cycle of SIB1 including CGI is 80 ms, and the SIB1 is configured to be repeatedly transmitted four times in a 20 ms cycle within 80 ms.

  Therefore, the mobile station UE can receive the SIB1 that has been repeatedly transmitted four times within 80 ms by performing a soft combining process.

  However, in the measurement gap patterns shown in FIGS. 7A and 7B, the reception timing of SIB1 in the mobile station UE is always “On Duration (from the connected radio base station eNB). In such a case, there is a problem that the mobile station UE cannot receive SIB1.

  Therefore, in LTE Release 9, there is a movement to provide a long measurement gap.

  For example, it is conceivable that a long measurement gap of one second order is provided, and the mobile station UE performs CGI reception or measurement of a different RAT cell in the measurement gap.

  FIG. 8 shows the handover operation when such a measurement gap is provided, and FIG. 9 shows the CSFB operation when such a measurement gap is provided.

  However, as shown in FIGS. 8 and 9, if the measurement gap is too long, uplink synchronization is lost during this time, and it is necessary to start over from the RACH procedure when transmitting the measurement report by the mobile station UE (FIG. 8). Steps S1019 to S1012, and Steps S2016 to S2019 of FIG. 9).

  Specifically, when the mobile station UE receives a TA (Timing Advance) command, it activates the TA timer, and when the TA timer expires without receiving the TA command again, uplink synchronization is lost. Therefore, it is necessary to start from the RACH procedure in order to establish uplink synchronization when transmitting uplink signals thereafter.

  Since the RACH procedure may cause a collision between a plurality of mobile stations UE, it may take a long time for the RACH procedure to succeed. If the RACH procedure is prolonged, there is a concern that the handover process and the CSFB procedure may be delayed.

  Accordingly, the present invention has been made in view of the above-described problems, and a mobile communication system and a mobile station that can prevent a delay while specifying a handover destination cell or a CSFB destination cell in a handover process or a CSFB procedure And it aims at providing a wireless base station.

  According to a first aspect of the present invention, there is provided a mobile station connected in the first cell, a first radio base station that manages the first cell, and a second radio base station that manages the second cell. The first radio base station and the second radio base station each include a transmitter configured to repeatedly transmit predetermined information in a subordinate cell at a predetermined period, A first radio base station comprising: a measurement gap determining unit configured to determine a measurement gap in the mobile station; the mobile station repeatedly in the second cell in the measurement gap A receiving unit configured to receive the predetermined information being transmitted and configured to determine that uplink synchronization has been lost if timing adjustment information is not received before the predetermined timer expires Ri has and a synchronization control section, the length of the measurement gap, in the predetermined period or more, and is summarized in that less than time until the predetermined timer expires.

  A second feature of the present invention is a mobile station connected in the first cell, which is repeatedly transmitted in the second cell in a measurement gap determined by the first radio base station that manages the first cell. The receiver configured to receive the predetermined information, and the uplink synchronization configured to determine that the uplink synchronization has been lost if the timing adjustment information is not received before the predetermined timer expires. The length of the measurement gap is not less than the predetermined period and less than the time until the predetermined timer expires.

  According to a third aspect of the present invention, there is provided a radio base station, wherein a transmission unit configured to repeatedly transmit predetermined information in a subordinate cell at a predetermined period, and a mobile station connected in the subordinate cell A measurement gap determining unit configured to determine a measurement gap, the length of the measurement gap being equal to or longer than the predetermined period and for maintaining uplink synchronization by the mobile station The gist is that the predetermined timer used is less than the time until expiration.

  As described above, according to the present invention, it is possible to provide a mobile communication system, a mobile station, and a radio base station that can prevent a delay while specifying a handover destination cell or a CSFB destination cell in a handover process or a CSFB procedure. can do.

1 is an overall configuration diagram of a mobile communication system according to a first embodiment of the present invention. FIG. 3 is a functional block diagram of a radio base station according to the first embodiment of the present invention. It is a figure which shows an example of the gap for a measurement determined by the wireless base station which concerns on the 1st Embodiment of this invention. FIG. 3 is a functional block diagram of a mobile station according to the first embodiment of the present invention. FIG. 3 is a sequence diagram showing an operation of the mobile communication system according to the first embodiment of the present invention. FIG. 3 is a sequence diagram showing an operation of the mobile communication system according to the first embodiment of the present invention. It is a figure which shows an example of the gap for a measurement used with the conventional mobile communication system. It is a sequence diagram which shows operation | movement of the conventional mobile communication system. It is a sequence diagram which shows operation | movement of the conventional mobile communication system.

(Mobile communication system according to the first embodiment of the present invention)
A mobile communication system according to a first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, in the mobile communication system according to the present embodiment, an LTE mobile communication system and a WCDMA mobile communication system are mixed.

  The LTE mobile communication system includes an exchange MME and radio base stations eNB # 1 and eNB # 2. The WCDMA mobile communication system includes an exchange SGSN, a radio network controller RNC, And a radio base station NB # 1.

  The frequency used in cell # 1 under radio base station eNB # 1, the frequency used in cell # 2 under radio base station eNB # 2, and the frequency used in cell # 3 under radio base station NB # 1 May be different or the same. In the present embodiment, it is assumed that the mobile station UE is being connected in the cell # 1.

  Since the function of the radio base station eNB # 1 and the function of the radio base station eNB # 2 are basically the same, the function will be described below as a representative of the radio base station eNB.

  As illustrated in FIG. 2, the radio base station eNB includes a measurement gap determination unit 11, a transmission unit 12, a reception unit 13, a handover processing unit 14, and a connection setting unit 15.

  The measurement gap determination unit 11 is configured to determine a measurement gap (Measurement Gap) in the connected mobile station UE in a cell under the radio base station eNB.

  For example, as shown in FIG. 3, the measurement gap determination unit 11 has a measurement gap length of 80 ms or more which is a transmission period (predetermined period) of the broadcast information (SIB1), and the TA timer expires. The measurement gap in the connected mobile station UE is determined so as to be less than the time up to.

  The transmission unit 12 is configured to transmit broadcast information in a cell under the radio base station eNB, or to transmit individual information and common information to the connected mobile station UE in the cell under the radio base station eNB. Has been.

  For example, the transmission unit 12 is configured to repeatedly transmit SIB1 that is broadcast information in a subordinate cell at a predetermined cycle (specifically, 80 ms).

  Alternatively, the transmission unit 12 transmits measurement control information (Measurement Control) including the measurement gap determined by the measurement gap determination unit 11 to the connected mobile station UE in the cell under the radio base station eNB. It is configured as follows.

  The receiving unit 13 is configured to receive information transmitted by the connected mobile station UE in a cell under the radio base station eNB.

  For example, the receiving unit 13 is configured to receive a measurement report or the like transmitted by the connected mobile station UE in a cell under the radio base station eNB.

  The handover processing unit 14 performs handover processing of a mobile station UE connected in a cell subordinate to the radio base station eNB to a cell subordinate to another radio base station, or a mobile station UE connected in a cell subordinate to another radio base station. Is configured to perform handover processing to cells under the radio base station eNB.

  The connection setting unit 15 is configured to perform a setting process for a connection with the mobile station UE in a subordinate cell.

  As shown in FIG. 4, the mobile station UE includes a reception unit 21, a transmission unit 22, a measurement unit 23, an uplink synchronization management unit 24, a RACH procedure execution unit 25, a handover processing unit 26, and a connection setting unit. 27 and a determination unit 28.

  The receiving unit 21 is configured to receive individual information and common information transmitted in the connected cell # 1.

  Alternatively, the receiving unit 21 is configured to receive predetermined information repeatedly transmitted in the cell # 2 or the cell # 3 specified by the measurement control information in the measurement gap specified by the measurement control information. .

  For example, the receiving unit 21 is configured to receive SIB1, which is broadcast information, a pilot signal, and the like as the predetermined information.

  The transmission unit 22 is configured to transmit various types of information to the radio base station eNB # 1 that manages the cell # 1 to which the mobile station UE is connected.

  For example, the transmission unit 22 is configured to transmit a measurement report including a measurement result by the measurement unit 23 described later.

  In addition, the transmission unit 22 includes “CGI” included in the SIB1 received by the reception unit 21 in the measurement report, and the radio base station eNB # that manages the cell # 1 to which the mobile station UE is connected. 1 may be configured to transmit.

  In addition, the transmission unit 22 includes “AI (Accessibility Indicator)” notified from the determination unit 28 described later in the measurement report, and the radio base station eNB # that manages the cell # 1 to which the mobile station UE is connected 1 may be configured to transmit.

  The measurement unit 23 is configured to perform measurement of the adjacent cell specified by the measurement control information received by the reception unit 21.

  Here, the measurement unit 23 uses the measurement gap specified by the measurement control information received by the reception unit 21 for a cell using a frequency different from the frequency of the cell # 1 to which the mobile station UE is connected. It is comprised so that it may measure in.

  The uplink synchronization management unit 24 is configured to manage whether uplink synchronization is established between the mobile station UE and the radio base station UE # 1.

  Here, the uplink synchronization management unit 24 is configured to use a TA timer (predetermined timer) in order to maintain such uplink synchronization.

  Specifically, the uplink synchronization management unit 24 activates the TA timer when it receives a TA command (timing adjustment information), and when it does not receive the TA command again before the TA timer expires, It is configured so that it is determined that is out of place.

  The RACH procedure execution unit 25 is configured to perform a RACH (Random Access Channel) procedure when information to be transmitted to the radio base station eNB # 1 occurs when uplink synchronization is lost.

  The handover processing unit 26 is configured to perform a handover process to another cell (cell # 2 or cell # 3) connected to the mobile station UE connected in the cell # 1.

  The connection setting unit 27 is configured to perform connection setting processing in each cell (cells # 1 to # 3).

  The determination unit 28 is configured to determine whether or not the mobile station UE has an access right to the cell # 2 based on the broadcast information received by the reception unit 21.

  Specifically, the determination unit 28 includes “CSG-ID (Closed Subscriber Group Identification)” included in the SIB1 received by the reception unit 21 in the “allowed CSG list” of the mobile station UE. It is configured to determine whether or not, generate “AI” indicating the determination result, and notify the transmission unit 22 of it.

  Hereinafter, the operation of the mobile communication system according to the present embodiment will be described with reference to FIG. 5 and FIG.

  1stly, with reference to FIG. 5, the operation | movement in case the mobile station UE hands over from cell # 1 to cell # 2 in the mobile communication system which concerns on this embodiment is demonstrated.

  As shown in FIG. 5, in step S101, the mobile station UE sends an uplink control signal to the radio base station eNB # 1 that manages the connected cell # 1 via a PUCCH (Physical Uplink Control Channel). Send.

  In step S102, the radio base station eNB # 1 transmits a TA command to the mobile station UE. Here, the mobile station UE starts the TA timer when receiving the TA command.

  In step S103, the mobile station UE transmits a measurement report including a measurement result of an adjacent cell (for example, cell # 2) specified by the measurement control information to the radio base station eNB # 1. In such measurement reports, neighboring cells are identified by PCI.

  In step S104, the radio base station eNB # 1 transmits measurement control information including a measurement gap to the mobile station UE.

  In step S105, the radio base station eNB # 2 transmits SIB1 via the BCCH in the subordinate cell # 2, and in step S106, the mobile station UE is transmitted in the cell # 2 in the measurement gap. SIB1 is received, and “CGI” and “CSG-ID” included in the SIB1 are acquired.

  Here, since the SIB1 is repeatedly transmitted at a cycle of 20 ms and the length of the measurement gap is 80 ms, the reception timing of the SIB1 in the mobile station UE always overlaps with “On Duration” of the mobile station UE. There is no problem of end.

  In step S107, the mobile station UE transmits an uplink control signal to the radio base station eNB # 1 via the PUCCH.

  In step S108, the radio base station eNB # 1 transmits a TA command to the mobile station UE. Here, when the mobile station UE receives the TA command, the mobile station UE restarts the TA timer.

  In step S109, the radio base station eNB # 2 transmits SIB1 via the BCCH in the subordinate cell # 2, and in step S110, the mobile station UE is transmitted in the cell # 2 in the measurement gap. SIB1 is received, and “CGI” and “CSG-ID” included in the SIB1 are acquired.

  In step S111, the mobile station UE transmits an uplink control signal to the radio base station eNB # 1 via the PUCCH.

  In step S112, the radio base station eNB # 1 transmits a TA command to the mobile station UE. Here, when the mobile station UE receives the TA command, the mobile station UE restarts the TA timer.

  In step S113, the radio base station eNB # 2 transmits SIB1 via the BCCH in the subordinate cell # 2, and in step S114, the mobile station UE is transmitted in the cell # 2 in the measurement gap. SIB1 is received, and “CGI” and “CSG-ID” included in the SIB1 are acquired.

  Here, the mobile station UE may acquire “CGI” and “CSG-ID” after performing the soft combining process on the SIB1 received in each of steps S106, S110, and S114.

  Since the length of the measurement gap is 80 ms, reception by the soft combining process is possible in the mobile station UE, the reception success probability is improved, and coverage can be expanded.

  In step S115, the mobile station UE releases the measurement gap designated in step S104.

  Control signals from the radio base station eNB # 1 can be reduced by autonomously releasing the measurement gap on the mobile station UE side. Further, it is possible to prepare for reception of a handover command (HO Command).

  In step S116, the mobile station UE transmits a scheduling request signal (Scheduling Request) to the radio base station eNB # 1 via the PUCCH.

  In step S117, the radio base station eNB # 1 transmits resource allocation information in the uplink to the mobile station UE via a PDCCH (Physical Downlink Control Channel).

  In step S118, the mobile station UE transmits a measurement report including “CGI” and “AI” for the above-described neighboring cell (for example, cell # 2) to the radio base station eNB # 1.

  In step S119, the radio base station eNB # 1 determines whether or not the mobile station UE should be handed over based on the measurement result and “AI” included in the measurement report.

  For example, when the radio quality of the cell # 2 satisfies a predetermined condition and the mobile station UE has an access right to the cell # 2, the radio base station eNB # 1 To hand over to cell # 2.

  On the other hand, if the radio quality of the cell # 2 satisfies the predetermined condition but the mobile station UE does not have access rights to the cell # 2, the radio base station eNB # 1 Interference measures such as handover to another cell using a frequency different from that of cell 1 or cell # 2 may be employed.

  In step S120, the mobile station UE transmits an uplink control signal to the radio base station eNB # 1 via the PUCCH. In step S121, the radio base station eNB # 1 “HO Required” is transmitted.

  In step S122, the radio base station eNB # 1 transmits a TA command to the mobile station UE. Here, when the mobile station UE receives the TA command, the mobile station UE restarts the TA timer.

  In step S123, the switching center MME determines whether or not the mobile station UE has an access right to the cell # 2, and the mobile station UE has an access right to the cell # 2. If it is determined, in step S124, "HO Preparation" is transmitted to the radio base station eNB # 2 that manages the cell # 2.

  In step S125, the radio base station eNB # 2 transmits “HO Preparation Ack” to the switching center MME, and in step S126, the switching center MME transmits “HO Required Ack” to the radio base station eNB # 1. Send.

  In step S127, the radio base station eNB # 1 transmits “HO Command” to the mobile station UE, and in step S128, the mobile station UE transmits “HO Complete” to the radio base station eNB # 2. To do.

  In Step S129, the radio base station eNB # 2 transmits “Path Switch” to the switching center MME, and in Step S130, the switching center MME transmits “Path Switch Ack” to the radio base station eNB # 2. Send.

  In step S131, the switching center MME transmits “Release Resource” to the radio base station eNB # 1.

  2ndly, with reference to FIG. 6, the operation | movement in case the mobile station UE CSFB from cell # 1 to cell # 3 in the mobile communication system which concerns on this embodiment is demonstrated.

  As illustrated in FIG. 6, in step S201, the mobile station UE transmits “RA Preamble” to the radio base station eNB # 1 that manages the connected cell # 1, and in step S202, the radio base station eNB # 1 transmits “RA Response (TA)” to the mobile station UE. Here, when the mobile station UE receives the “RA Response (TA)”, the mobile station UE restarts the TA timer.

  In step S203, the mobile station UE transmits “RRC Connection Request” to the radio base station eNB # 1, and in step S204, the radio base station eNB # 1 transmits “RRC Connection Setup” to the mobile station UE. Send.

  In step S205, the mobile station UE transmits “RRC Connection Request” including “NAS Extended Service Request” to the radio base station eNB # 1.

  In step S206, the radio base station eNB # 1 transmits “RRC Connection Request” including “NAS Extended Service Request” to the switching center MME.

  In step S207, the switching center MME transmits “S1 Initial Context Setup (CSFB)” to the radio base station eNB # 1.

  The radio base station eNB # 1 transmits “RRC SMC” to the mobile station UE in step S208, and transmits “RRC Reconfiguration” in step S209.

  In step S210, the mobile station UE transmits “RRC SMC Complete” to the radio base station eNB # 1, and transmits “RRC Reconfiguration Complete” in step S211.

  In step S212, the radio base station eNB # 1 transmits “S1 Setup Comme” to the exchange MME.

  In step S213, the mobile station UE searches for an adjacent cell in the measurement gap specified by the measurement control information, and measures the adjacent cell.

  In step S214, the mobile station UE transmits an uplink control signal to the radio base station eNB # 1 via the PUCCH.

  In step S215, the radio base station eNB # 1 transmits a TA command to the mobile station UE. Here, when the mobile station UE receives the TA command, the mobile station UE restarts the TA timer.

  In step S216, the mobile station UE searches for an adjacent cell in the measurement gap specified by the measurement control information, and measures the adjacent cell.

  In step S217, the mobile station UE transmits an uplink control signal to the radio base station eNB # 1 via the PUCCH.

  In step S218, the radio base station eNB # 1 transmits a TA command to the mobile station UE. Here, when the mobile station UE receives the TA command, the mobile station UE restarts the TA timer.

  In step S219, the mobile station UE searches for an adjacent cell in the measurement gap specified by the measurement control information and performs measurement of the adjacent cell. In step S220, the mobile station UE releases the measurement gap. To do.

  Control signals from the radio base station eNB # 1 can be reduced by autonomously releasing the measurement gap on the mobile station UE side. Moreover, it can prepare for reception of a handover command (MobilityFromEUTRA).

  In step S221, the mobile station UE transmits a scheduling request signal (Scheduling Request) to the radio base station eNB # 1 via the PUCCH.

  In step S222, the radio base station eNB # 1 transmits resource allocation information in the uplink to the mobile station UE via the PDCCH.

  In step S223, the mobile station UE transmits a measurement report including the cell ID and the radio quality for the above-described neighboring cell (for example, the cell # 2) to the radio base station eNB # 1.

  Here, the radio base station eNB # 1 should perform CSFB from the cell # 1 to the cell # 3 only when the mobile station UE has an access right to the cell # 3. You may determine that there is.

  In step S224, the radio base station eNB # 1 transmits “S1 Relocation Required” to the switching center MME. In step S225, the switching base station MME accommodates the radio base station NB # 1 that manages the cell # 3. "Relocation Required" is transmitted to the exchange SGSN and the radio network controller RNC.

  In step S226, the switching center SGSN and the radio network controller RNC transmit “Relocation Ack” to the switching center MME. In step S227, the switching center MME transmits “S1 Relocation to the radio base station eNB # 1. Ack "is transmitted.

  In step S228, the radio base station eNB # 1 transmits “MobilityFromEUTRA” to the mobile station UE.

  In step S229, the inter-RAT handover (inter-RAT handover) of the mobile station UE from the cell # 1 to the cell # 3 is performed. In step S230, the CS RAB is transmitted between the mobile station UE and the cell # 3. (Radio Access Bearer) is set.

  According to the mobile communication system according to the present embodiment, the length of the measurement gap is equal to or longer than the transmission period of predetermined information (for example, a UMTS or GSM pilot signal) required for measurement of different RAT cells. Since it is configured, the reception timing of the predetermined information in the mobile station UE always overlaps with “On Duration” of the mobile station UE, and the problem that the mobile station UE cannot receive the predetermined information is solved. Can do.

  Further, according to the mobile communication system according to the present embodiment, the length of the measurement gap is configured to be less than the time until the TA timer expires, and therefore, uplink synchronization is performed during the measurement gap period. And the RACH procedure is always performed at the time of transmission of the next uplink signal, so that the problem that the handover process and the CSFB procedure are delayed can be solved.

  The characteristics of the present embodiment described above may be expressed as follows.

  The first feature of the present embodiment is that the mobile station UE connected in the cell # 1 (first cell), the radio base station eNB # 1 (first radio base station) that manages the cell # 1, and the cell # Mobile station 2 (second cell) that manages radio base station eNB # 2 (or radio base station NB # 1 that manages cell # 3 (second cell)) (second radio base station) In the communication system, the radio base station eNB # 1 and the radio base station eNB # 2 (or the radio base station NB # 1) are configured to repeatedly transmit predetermined information in subordinate cells in a predetermined cycle. The radio base station eNB # 1 includes a measurement gap determining unit 11 configured to determine a measurement gap in the mobile station UE, and the mobile station UE In the measurement gap And the TA command (timing) until the TA 21 (predetermined timer) expires and the receiver 21 configured to receive the predetermined information repeatedly transmitted in the cell # 2 (or cell # 3). And the uplink synchronization management unit 24 configured to determine that uplink synchronization has been lost when the adjustment information is not received, and the length of the measurement gap is equal to or longer than a predetermined period, and The gist is that it is less than the time until the TA timer expires.

  In the first feature of the present embodiment, the receiving unit 21 is configured to receive broadcast information repeatedly transmitted in the cell # 2 in the measurement gap, and the mobile station UE is included in the broadcast information. A measurement report (Measurement Report) including the “CGI (cell ID)” may be further provided to the radio base station eNB # 1.

  In the first feature of the present embodiment, the mobile station UE is configured to determine whether or not the mobile station UE has an access right to the cell # 2 based on the broadcast information received by the receiving unit 21. The transmission unit 22 may further be configured to transmit a measurement report including information (AI) indicating presence / absence of an access right to the radio base station eNB # 1.

  In the first feature of the present embodiment, the mobile station UE measures the radio quality in the cell # 2 (or cell # 3) based on the information received by the receiving unit 21 in the measurement gap. You may further comprise the comprised measurement part 23 and the transmission part 22 comprised so that the measurement report containing a measurement result may be transmitted with respect to radio base station eNB # 1.

  The second feature of the present embodiment is the mobile station UE being connected in the cell # 1, and in the measurement gap determined by the radio base station eNB # 1 that manages the cell # 1, the cell # 2 (or If the TA command is not received before the TA timer expires and the receiving unit 21 configured to receive the predetermined information repeatedly transmitted in the cell # 3), it is determined that the uplink synchronization has been lost. The uplink synchronization management unit 24 is configured so that the length of the measurement gap is not less than a predetermined period and less than the time until the TA timer expires. .

  In the second feature of the present embodiment, the receiving unit 21 is configured to receive broadcast information that is repeatedly transmitted in the cell # 2 in the measurement gap, and the CGI included in the broadcast information is received. You may further comprise the transmission part 22 comprised so that the measurement report containing may be transmitted with respect to radio base station eNB # 1.

  The second feature of the present embodiment is further provided with a determination unit configured to determine whether or not the mobile station UE has an access right to the cell # 2 based on the broadcast information received by the reception unit 21. And the transmission part 22 may be comprised so that the measurement report containing the information which shows the presence or absence of an access right may be transmitted with respect to radio base station eNB # 1.

  In the second feature of the present embodiment, the measurement is configured to measure the radio quality in the cell # 2 (or cell # 3) based on the information received by the receiving unit 21 in the measurement gap. You may further comprise the part 23 and the transmission part 22 comprised so that the measurement report containing a measurement result may be transmitted with respect to radio base station eNB # 1.

  A third feature of the present embodiment is a radio base station eNB, which is configured to repeatedly transmit predetermined information in a subordinate cell at a predetermined cycle, and being connected in the subordinate cell A measurement gap determining unit 11 configured to determine a measurement gap in the mobile station UE, the length of the measurement gap being equal to or longer than a predetermined period, and maintaining uplink synchronization by the mobile station UE The gist of the invention is that the TA timer used for the time is less than the time until expiration.

  In the third feature of the present embodiment, the measurement gap may be autonomously released when the measurement report is started.

  Note that the operations of the radio base station eNB / NB, the mobile station UE, and the switching center MME / SGSN described above may be performed by hardware, may be performed by a software module executed by a processor, or both. It may be implemented by a combination of

  The software module includes a RAM (Random Access Memory), a flash memory, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electronically Erasable and Programmable ROM, a hard disk, a registerable ROM, a hard disk). Alternatively, it may be provided in a storage medium of an arbitrary format such as a CD-ROM.

  Such a storage medium is connected to the processor so that the processor can read and write information from and to the storage medium. Further, such a storage medium may be integrated in the processor. Such a storage medium and processor may be provided in the ASIC. Such an ASIC may be provided in the radio base station eNB / NB, the mobile station UE, or the exchange MME / SGSN. Further, the storage medium and the processor may be provided in the radio base station eNB / NB, the mobile station UE, and the exchange MME / SGSN as discrete components.

  Although the present invention has been described in detail using the above-described embodiments, it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

eNB ... radio base station UE ... mobile station 11 ... measurement gap determining unit 12, 22 ... transmitting unit 13, 21 ... receiving unit 14, 26 ... handover processing unit 15, 27 ... connection setting unit 23 ... measuring unit 24 ... uplink synchronization Management unit 25 ... RACH procedure execution unit 28 ... determination unit

Claims (10)

A mobile communication system comprising a mobile station connected in the first cell, a first radio base station that manages the first cell, and a second radio base station that manages the second cell,
The first radio base station and the second radio base station are
A transmitter configured to repeatedly transmit predetermined information in a subordinate cell at a predetermined period;
The first radio base station is
Comprising a measurement gap determining unit configured to determine a measurement gap in the mobile station;
The mobile station
A receiver configured to receive predetermined information repeatedly transmitted in the second cell in the measurement gap;
An uplink synchronization management unit configured to determine that uplink synchronization has been lost if timing adjustment information is not received before the predetermined timer expires, and
The length of the measurement gap is not less than the predetermined period and less than the time until the predetermined timer expires. The receiving unit is configured to receive broadcast information that is repeatedly transmitted in the second cell in the measurement gap,
The mobile station further comprises a transmitter configured to transmit a measurement report including a cell ID included in the broadcast information to the first radio base station. Item 4. The mobile communication system according to Item 1. The mobile station further includes a determination unit configured to determine whether the mobile station has an access right to the second cell based on broadcast information received by the reception unit,
The mobile communication system according to claim 2, wherein the transmission unit is configured to transmit a measurement report including information indicating presence / absence of the access right to the first radio base station. . The mobile station is configured to measure the radio quality in the second cell based on the information received by the receiver in the measurement gap; and
The mobile communication system according to claim 1, further comprising a transmission unit configured to transmit a measurement report including the measurement result to the first radio base station. A mobile station connected in the first cell,
A receiver configured to receive predetermined information repeatedly transmitted in a second cell in a measurement gap determined by a first radio base station that manages the first cell;
An uplink synchronization management unit configured to determine that uplink synchronization has been lost if timing adjustment information is not received before the predetermined timer expires, and
The length of the measurement gap is not less than the predetermined period and less than the time until the predetermined timer expires. The receiving unit is configured to receive broadcast information that is repeatedly transmitted in the second cell in the measurement gap,
The transmitter according to claim 5, further comprising a transmitter configured to transmit a measurement report including a cell ID included in the broadcast information to the first radio base station. Mobile station. A determination unit configured to determine whether the mobile station has an access right to the second cell based on the broadcast information received by the reception unit;
The mobile station according to claim 6, wherein the transmission unit is configured to transmit a measurement report including information indicating presence / absence of the access right to the first radio base station. A measuring unit configured to measure radio quality in the second cell based on information received by the receiving unit in the measurement gap;
The mobile station according to claim 5, further comprising: a transmission unit configured to transmit a measurement report including the measurement result to the first radio base station. A transmitter configured to repeatedly transmit predetermined information in a subordinate cell at a predetermined period;
A measurement gap determining unit configured to determine a measurement gap in a connected mobile station in a subordinate cell;
The length of the measurement gap is equal to or longer than the predetermined period, and is less than a time until a predetermined timer used for maintaining uplink synchronization by the mobile station expires. Bureau.   The mobile station according to claim 5, wherein the mobile station is configured to autonomously release a measurement gap when starting the measurement report.

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